Graduated compression stockings are snug-fitting elastic garments that apply the most pressure at your ankle and gradually decrease that pressure as they move up your leg. This design pushes blood upward toward your heart, preventing it from pooling in your lower legs. They’re used for everything from preventing blood clots after surgery to relieving tired, swollen legs after a long day on your feet.
How the Pressure Gradient Works
Unlike a regular tight sock that squeezes evenly, graduated compression stockings follow a specific pressure profile. The strongest squeeze is at the ankle, and it tapers off as the stocking rises toward the knee or thigh. One well-studied pressure profile applies 18 mmHg at the ankle, 14 mmHg at the mid-calf, and 8 mmHg at the knee. That descending gradient was found to increase the speed of blood flow in deep leg veins by 75%.
This matters because slow-moving blood is more likely to clot. The stockings work on two fronts: they speed up venous return so blood doesn’t stagnate, and they prevent the vein walls from stretching outward under pressure. When veins overstretch, the inner lining can tear slightly, which activates clotting factors. By keeping veins at a narrower diameter, graduated compression reduces that risk while also improving lymphatic drainage, the system that clears excess fluid from your tissues.
Compression Levels and What They’re For
Compression stockings come in several pressure ranges, measured in millimeters of mercury (mmHg). The number tells you how much squeeze the stocking delivers at the ankle, its tightest point.
- 10 to 15 mmHg (light compression): Effective for preventing mild swelling from prolonged sitting or standing. This is the level most people start with for everyday leg fatigue or long flights.
- 15 to 20 mmHg (moderate compression): A step up for occupational swelling, minor varicose veins, and travel-related leg discomfort. Available over the counter without a prescription.
- 20 to 30 mmHg (firm compression): The most commonly prescribed medical grade. Research shows this range is more effective than lighter stockings for reducing swelling, especially if you sit for long stretches at work. It’s also used for moderate varicose veins, post-surgical recovery, and preventing blood clots.
- 30 to 40 mmHg and above: Reserved for more serious venous conditions like severe chronic venous insufficiency, active leg ulcers, or significant lymphatic swelling. These typically require a prescription and professional fitting.
For most healthy people dealing with leg swelling from a desk job or long travel days, stockings in the 10 to 20 mmHg range are a good starting point. If you have a diagnosed venous condition, higher pressures are likely needed.
Knee-High vs. Thigh-High vs. Waist-High
Graduated compression stockings come in three main lengths: knee-high (the most common), thigh-high, and waist-high (pantyhose style). Your choice depends on where your symptoms are and what you can tolerate wearing.
Knee-high stockings cover the area where blood pooling and swelling are most common, and they’re far easier to put on and keep in place throughout the day. Thigh-high stockings cover more of the leg but tend to roll down, which can create a tourniquet effect at the thigh and actually restrict blood flow. A meta-analysis comparing knee-high to thigh-high stockings for blood clot prevention found no significant difference in effectiveness. So unless your doctor specifically recommends a longer length for thigh or groin-area concerns, knee-high stockings are the practical choice for most people.
How Effective Are They at Preventing Blood Clots?
The evidence for graduated compression stockings in surgical settings is substantial. Used alone, they reduce the incidence of deep vein thrombosis (DVT) by roughly 60%. In general surgical patients, the relative risk drops by 64%, and in patients undergoing total hip replacement, by 57%. When combined with blood-thinning medication or mechanical compression devices, that reduction climbs to as high as 85%.
These numbers come from hospitalized patients, who face higher clot risk than the general population. But the underlying principle applies more broadly: if you’re in a situation where your legs will be still for hours, whether after surgery, during a long flight, or while recovering from an illness in bed, graduated compression stockings meaningfully reduce your clot risk.
Who Should Not Wear Them
Compression stockings are not safe for everyone. The primary concern is peripheral artery disease (PAD), a condition where the arteries in your legs are already narrowed. Adding external compression on top of poor arterial flow can reduce blood supply to the foot and cause tissue damage. Current guidelines consider compression therapy contraindicated when the ankle-brachial index (a ratio comparing blood pressure in your ankle to your arm) falls below 0.5 or when ankle arterial pressure drops below 60 mmHg.
Other situations where compression stockings can cause problems include skin infections or open wounds on the legs, severe nerve damage that prevents you from feeling discomfort, and certain forms of heart failure where pushing more fluid back toward the heart could be harmful. If you have any of these conditions, get clearance before using them.
Getting the Right Fit
A poorly fitting compression stocking is worse than no stocking at all. Too loose and it won’t deliver therapeutic pressure. Too tight and it can cut off circulation, especially if it bunches or rolls at the top.
Take your measurements first thing in the morning, before your legs have a chance to swell. Sit with your feet flat on the floor and use a soft measuring tape on bare skin. For knee-high stockings, you’ll need the circumference of your ankle just above the bone, the circumference of your calf at its widest point, and the length from the floor to just below your knee. For thigh-high stockings, you’ll add your thigh circumference and the full leg length.
Most brands provide sizing charts based on these measurements. If your measurements fall between two sizes or if one leg is noticeably larger than the other, a medical supply store or vein specialist can help with custom fitting.
Putting Them On (Without a Struggle)
The tighter the stocking, the harder it is to pull on, especially if you have limited mobility in your hands or hips. A few practical tricks make a real difference.
Sit on a firm surface like a bed or sturdy chair where you can comfortably reach your feet. Rubber dishwashing gloves give you a much better grip on the fabric and help you smooth out wrinkles without snagging the material with fingernails. If you choose open-toe stockings, you can use a “slippy sock,” a thin, silky sleeve that goes over your foot first. You slide the compression stocking over it, then pull the slippy sock out through the toe opening once the stocking is in place. This eliminates the hardest part: getting the tight fabric over your heel. Some brands include these aids in the box.
For people who can’t bend forward easily, frame-style donning devices hold the stocking open so you can step into it and slide it up without reaching down. These are widely available at medical supply stores.
Care and Replacement
Compression stockings lose their elasticity over time, which means the therapeutic pressure they deliver gradually weakens. Plan to replace them every 3 to 6 months, even if they look fine. Hand washing in cool water with mild soap and air drying extends their life; machine washing and heat from a dryer break down the elastic fibers faster. If you wear them daily, having two pairs in rotation lets each pair rest between wearings and helps them hold their compression longer.